Preparation method of flaky hollow TS-1 molecular sieve for phenol hydroxylation, molecular sieve and application
By preparing sheet-like hollow TS-1 molecular sieves, the problems of high mass transfer resistance and insufficient six-coordinate titanium content were solved, achieving highly efficient catalytic hydroxylation of phenol, reducing costs and improving catalytic performance.
Patent Information
- Application Number
- CN202510859321.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-25
- Publication Date
- 2025-11-21
AI Technical Summary
Existing technologies make it difficult to prepare TS-1 molecular sieves rich in six-coordinated titanium, and microporous TS-1 molecular sieves exhibit high mass transfer resistance and unsatisfactory catalytic effects in phenol hydroxylation reactions.
A specific process was employed to synthesize sheet-like hollow TS-1 molecular sieves, including the use of raw materials such as tetraethyl orthosilicate, tetrabutyl titanate, tetrapropylammonium hydroxide, and N,N-dimethylformamide, through hydrothermal crystallization and calcination to prepare sheet-like hollow TS-1 molecular sieves rich in six-coordinated titanium.
It reduced mass transfer resistance, improved catalytic activity, increased the proportion of six-coordinate titanium active sites, improved the conversion and selectivity of phenol hydroxylation reaction, and reduced synthesis cost.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of molecular sieve synthesis technology, and in particular to a method for preparing a sheet-like hollow TS-1 molecular sieve for phenol hydroxylation, the molecular sieve itself, and its application. Background Technology
[0002] Titanium-containing molecular sieves have been widely used as heteroatom molecular sieve catalysts for decades, such as TS-1, TS-2, Ti-Beta, Ti-MWW, and Ti-MCM-22. The TS-1 / H2O2 system has attracted much attention due to its excellent catalytic performance in epoxidation, hydroxylation, and oxidative desulfurization, as well as the environmentally friendly and pollution-free reaction process and the reusability of the molecular sieve.
[0003] patent[ 1 This report marks the first synthesis of TS-1. The raw TS-1 powder was obtained via a typical hydrothermal synthesis strategy using tetraethyl orthosilicate (TEOS) as the silicon source, tetraethyl titanate (TBOT) as the titanium source, and tetrapropylammonium hydroxide (TPAOH) as the template agent. However, this strategy requires high purity of the raw materials due to the presence of Na... + K + Alkali metal ions significantly influence this synthetic strategy, making it difficult to obtain TS-1 molecular sieves with high catalytic performance. To date, various Ti active sites with different coordination environments have been discovered in TS-1 molecular sieves. Besides the predominantly tetracoordinate (TiO4) active site, other noteworthy active substances have been found, including tetracoordinate binuclear Ti, tetracoordinate Ti(OSi)3OH, pentacoordinate TiO5 (Ti(OH)2(OSi)3), and hexacoordinate TiO6 (Ti(OH2)2(OH)2(OSi)2 and Ti(OH)4(OSi)2). It has been demonstrated that hexacoordinate titanium active species exhibit superior activity in catalytic reactions compared to traditional tetracoordinate titanium active species. Therefore, how to prepare TS-1 rich in hexacoordinate titanium is a challenging problem of significant practical importance.
[0004] Furthermore, in the hydroxylation reaction of phenol, the microporous TS-1 molecular sieve synthesized by traditional processes suffers from high mass transfer resistance, making it difficult to achieve ideal catalytic performance. Shortening the molecular diffusion path is an effective way to reduce mass transfer resistance in the reaction process. Therefore, the directional design of molecular sieve morphology (such as constructing hollow structures, plate-like structures, hierarchical porous structures, and nanoscale zeolite molecular sieves) has been proven to be an effective strategy to reduce this mass transfer resistance. Summary of the Invention
[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a sheet-like hollow TS-1 molecular sieve for phenol hydroxylation, the molecular sieve itself, and its applications.
[0006] The technical solution adopted by this invention to solve its technical problem is:
[0007] A method for preparing a sheet-like hollow TS-1 molecular sieve for phenol hydroxylation includes the following synthetic steps:
[0008] (1) Add tetraethyl orthosilicate dropwise to an aqueous solution containing tetrapropylammonium hydroxide;
[0009] (2) After the above solution becomes clear, add the solution containing tetrabutyl titanate and isopropanol dropwise to allow for complete hydrolysis;
[0010] (3) Stir the obtained clear solution in a constant temperature water bath to remove alcohol for 1 hour;
[0011] (4) After the alcohol removal is completed, N,N-dimethylformamide is added to the resulting solution;
[0012] (5) The obtained solution was placed in a kettle, and after hydrothermal crystallization, the crystallized product was obtained. Finally, centrifugation, drying and calcination were performed to obtain the parent sheet-like TS-1 molecular sieve.
[0013] (6) Dissolve the parent TS-1 molecular sieve in an aqueous solution of tetrapropylammonium bromide and ethanolamine to obtain a precursor solution;
[0014] (7) The obtained solution is placed in a kettle, and after hydrothermal crystallization, a crystallized product is obtained. Finally, it is centrifuged, dried and calcined to obtain a sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium, which is the sheet-like hollow TS-1 molecular sieve used for phenol hydroxylation.
[0015] Further, in step (1), the aqueous solution containing tetrapropylammonium hydroxide has a mass concentration of 25%, the water is deionized water, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate (calculated as SiO2) is 0.1 to 0.5:1, and the molar ratio of deionized water to tetraethyl orthosilicate is 20 to 50:1.
[0016] Further, in step (2), the mass ratio of tetrabutyl titanate to isopropanol is 0.2-0.3:2.0-3.0, the mass ratio of tetrabutyl titanate to tetraethyl orthosilicate in step (1) is 1:30-50, and the mass ratio of tetrabutyl titanate to tetrapropylammonium hydroxide in step (1) is 1:10-20.
[0017] Alternatively, in step (3), the alcohol removal temperature is 50–90°C and the dissolution time is 2–6 h.
[0018] Furthermore, in step (4), the molar ratio of N,N-dimethylformamide to tetraethyl orthosilicate (calculated as SiO2) in step (1) is 0.2 to 1.2:1, and the mass ratio of N,N-dimethylformamide to tetrapropylammonium hydroxide in step (1) is 0.04 to 0.2:1.
[0019] Further, in step (6), the mass ratio of tetrapropylammonium bromide to the parent flaky TS-1 molecular sieve is 0.5 to 1.0:1, the mass ratio of ethanolamine to the parent flaky TS-1 molecular sieve is 1 to 2:1, the water is deionized water, and the mass ratio of deionized water to the parent flaky TS-1 molecular sieve is 20 to 40:1.
[0020] Alternatively, in step (6), the dissolution temperature is 40–80°C and the dissolution time is 2–6 h.
[0021] Furthermore, the hydrothermal crystallization temperature in steps (5) and (7) is 100–200°C and the time is 24–72 h; the calcination temperature in steps (5) and (7) is 500–600°C and the time is 2–8 h.
[0022] The sheet-like hollow TS-1 molecular sieve was prepared by the method described above.
[0023] The application of the sheet-like hollow TS-1 molecular sieve as described above in the catalytic hydroxylation reaction of phenol.
[0024] The method for catalyzing the hydroxylation reaction of phenol using the sheet-like hollow TS-1 molecular sieve described above includes the following steps:
[0025] 1) Mix TS-1 molecular sieve, phenol, and methanol evenly in a round-bottom flask; wherein the mass ratio of TS-1 molecular sieve to phenol is 1:10, and the mass ratio of phenol to methanol is 1:4.
[0026] 2) Place the round-bottom flask in a water bath and stir at 500-1000 rpm until it reaches 50-80°C. Add hydrogen peroxide to start the reaction at 50-80°C under normal pressure for 4-6 hours.
[0027] The mass ratio of phenol to hydrogen peroxide is 1:0.4.
[0028] 3) After the reaction is complete, cool the mixture rapidly to room temperature in a cold water bath.
[0029] The advantages and positive effects of this invention are as follows:
[0030] 1. The method of the present invention is low in cost and simple to operate, and can rapidly synthesize sheet-like hollow TS-1 molecular sieves. The sheet-like morphology and hollow structure improve the diffusion mass transfer rate and have abundant six-coordinate titanium active sites, exhibiting excellent catalytic activity in the epoxidation of 1-hexene, epoxidation of cyclohexene, epoxidation of propylene, and hydroxylation of phenol.
[0031] 2. The method of the present invention can further increase the proportion of six-coordinate titanium active sites in the sample by strategically controlling the thickness of the molecular sieve along the b-axis and the microenvironment of the titanium active sites, so as to prepare molecular sieves with higher catalytic activity for industrial applications.
[0032] 3. In the method of the present invention, the raw materials used in the post-processing step are tetrapropylammonium bromide and ethanolamine, which can be recycled as mother liquor, greatly reducing the synthesis cost and facilitating its widespread industrial application. Attached Figure Description
[0033] Figure 1 This is a TEM image of the sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium prepared in this invention.
[0034] Figure 2 The XRD pattern of the sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium prepared in this invention is shown.
[0035] Figure 3 The UV-vis spectrum of the sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium prepared in this invention.
[0036] Figure 4 The UV-Raman spectrum of the sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium prepared in this invention is shown. Detailed Implementation
[0037] The present invention will be further described below with reference to the embodiments. The following embodiments are descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.
[0038] The various experimental operations involved in the specific embodiments are all conventional techniques in the field. For parts not specifically annotated in this document, those skilled in the art can refer to various commonly used reference books, scientific and technological documents or related instructions and manuals prior to the filing date of this invention to carry out the operations.
[0039] A method for preparing a sheet-like hollow TS-1 molecular sieve for phenol hydroxylation includes the following synthetic steps:
[0040] (1) Add tetraethyl orthosilicate dropwise to an aqueous solution containing tetrapropylammonium hydroxide;
[0041] (2) After the above solution becomes clear, add the solution containing tetrabutyl titanate and isopropanol dropwise to allow for complete hydrolysis;
[0042] (3) Stir the obtained clear solution in a constant temperature water bath to remove alcohol for 1 hour;
[0043] (4) After the alcohol removal is completed, N,N-dimethylformamide is added to the resulting solution;
[0044] (5) The obtained solution was placed in a kettle, and after hydrothermal crystallization, the crystallized product was obtained. Finally, centrifugation, drying and calcination were performed to obtain the parent sheet-like TS-1 molecular sieve.
[0045] (6) Dissolve the parent TS-1 molecular sieve in an aqueous solution of tetrapropylammonium bromide and ethanolamine to obtain a precursor solution;
[0046] (7) The obtained solution is placed in a kettle, and after hydrothermal crystallization, a crystallized product is obtained. Finally, it is centrifuged, dried and calcined to obtain a sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium, which is the sheet-like hollow TS-1 molecular sieve used for phenol hydroxylation.
[0047] Preferably, in step (1), the aqueous solution containing tetrapropylammonium hydroxide has a mass concentration of 25%, the water is deionized water, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate (calculated as SiO2) is 0.1 to 0.5:1, and the molar ratio of deionized water to tetraethyl orthosilicate is 20 to 50:1.
[0048] Preferably, in step (2), the mass ratio of tetrabutyl titanate to isopropanol is 0.2-0.3:2.0-3.0, the mass ratio of tetrabutyl titanate to tetraethyl orthosilicate in step (1) is 1:30-50, and the mass ratio of tetrabutyl titanate to tetrapropylammonium hydroxide in step (1) is 1:10-20.
[0049] Alternatively, in step (3), the alcohol removal temperature is 50–90°C and the dissolution time is 2–6 h.
[0050] Preferably, the molar ratio of N,N-dimethylformamide in step (4) to tetraethyl orthosilicate (calculated as SiO2) in step (1) is 0.2 to 1.2:1, and the mass ratio of N,N-dimethylformamide in step (4) to tetrapropylammonium hydroxide in step (1) is 0.04 to 0.2:1.
[0051] Preferably, in step (6), the mass ratio of tetrapropylammonium bromide to the parent flaky TS-1 molecular sieve is 0.5 to 1.0:1, the mass ratio of ethanolamine to the parent flaky TS-1 molecular sieve is 1 to 2:1, the water is deionized water, and the mass ratio of deionized water to the parent flaky TS-1 molecular sieve is 20 to 40:1.
[0052] Alternatively, in step (6), the dissolution temperature is 40–80°C and the dissolution time is 2–6 h.
[0053] Preferably, the hydrothermal crystallization temperature in steps (5) and (7) is 100-200℃ and the time is 24-72h; the calcination temperature in steps (5) and (7) is 500-600℃ and the time is 2-8h.
[0054] The sheet-like hollow TS-1 molecular sieve was prepared by the method described above.
[0055] The application of the sheet-like hollow TS-1 molecular sieve as described above in the catalytic hydroxylation reaction of phenol.
[0056] The method for catalyzing the hydroxylation reaction of phenol using the sheet-like hollow TS-1 molecular sieve described above includes the following steps:
[0057] 1) Mix TS-1 molecular sieve, phenol, and methanol evenly in a round-bottom flask; wherein the mass ratio of TS-1 molecular sieve to phenol is 1:10, and the mass ratio of phenol to methanol is 1:4.
[0058] 2) Place the round-bottom flask in a water bath and stir at 500-1000 rpm until it reaches 50-80°C. Add hydrogen peroxide to start the reaction at 50-80°C under normal pressure for 4-6 hours.
[0059] The mass ratio of phenol to hydrogen peroxide is 1:0.4.
[0060] 3) After the reaction is complete, cool the mixture rapidly to room temperature in a cold water bath.
[0061] Specifically, the relevant preparation and testing methods are as follows:
[0062] Example 1
[0063] A method for preparing TS-1 molecular sieve for phenol hydroxylation, the specific steps of which are as follows:
[0064] (1) Weigh 4.287g of tetrapropylammonium hydroxide (TPAOH) and prepare a solution with 9.745g of deionized water. Add 3g of tetraethyl orthosilicate to the solution and stir at room temperature until clear.
[0065] (2) Weigh 0.0613g of tetrabutyl titanate and add it to 0.8g of isopropanol, then add it dropwise to the solution in step (1) and stir at room temperature for 2 hours.
[0066] (3) Transfer the system to an 80℃ water bath and stir for 2 hours.
[0067] (4) Weigh 0.632g of N,N-dimethylformamide (DMF) and add it to the solution in step (4), and stir at room temperature for 1h.
[0068] (5) The system was transferred to a reaction vessel and hydrothermally heated at 170°C for 24 h. After cooling to room temperature, it was centrifuged at 12500 rpm for 3 min with a large amount of deionized water and anhydrous ethanol. The mixture was washed until the pH was neutral and dried at 100°C for 12 h. The parent molecular sieve was obtained by calcination at 550°C for 6 h.
[0069] (6) Weigh 0.383g of tetrapropylammonium bromide and 0.51g of ethanolamine and add them to 14.4mL of deionized water to prepare a solution. Stir at room temperature until clear.
[0070] (7) Weigh 0.5g of the seed crystals prepared in step (5) and add them to the solution in step (6). Stir at room temperature for 1 hour.
[0071] (8) The system was transferred to a reaction vessel and hydrothermally heated at 170°C for 24 h. After cooling to room temperature, it was centrifuged at 12500 rpm for 3 min with a large amount of deionized water and anhydrous ethanol. The mixture was washed until the pH was neutral and dried at 100°C for 12 h. Calcination at 550°C for 6 h yielded a sheet-like hollow TS-1 molecular sieve rich in hexacoordinate titanium.
[0072] The specific steps of the method for catalytic hydroxylation of phenol using the sheet-like hollow TS-1 molecular sieve described above are as follows:
[0073] 1) Weigh 0.2000g of TS-1 molecular sieve, 2.000g of phenol, and 8.000g of methanol, and mix the above system evenly in a round-bottom flask.
[0074] 2) Place the round-bottom flask in a water bath and stir. After heating to 60°C, add 7 mmol of hydrogen peroxide (the molar ratio of phenol to hydrogen peroxide is 3:1). Start the reaction at 60°C, with a stirring speed of 600 rpm and atmospheric pressure, and react for 6 hours.
[0075] 3) After the reaction is complete, cool the mixture rapidly to room temperature in a cold water bath to obtain the reaction system.
[0076] The relevant tests are as follows:
[0077] 1. Performance testing of the sheet-like hollow TS-1 molecular sieve obtained in Example 1 of this invention
[0078] Figure 1 The image shows a transmission electron microscope (TEM) image of the sheet-like hollow TS-1 molecular sieve prepared in Example 1. The results show that the prepared material does indeed have a sheet-like morphology and is rich in mesopores with a pore size distribution of 2–200 nm.
[0079] Figure 2 The XRD pattern of the sheet-like hollow TS-1 molecular sieve prepared in Example 1 shows that the material has typical MFI structural characteristic peaks and the modified material retains the original crystal form and relative crystallinity.
[0080] Figure 3 The UV-vis spectrum of the sheet-like hollow TS-1 molecular sieve prepared in Example 1 shows that the sample contains 60-70% hexacoordinate titanium, 25-30% tetracoordinate titanium, and a small amount of anatase TiO2.
[0081] Figure 4 The UV-Raman spectrum of the sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium prepared in Example 1 shows that the sample has abundant six-coordinated titanium active sites.
[0082] 2. The relevant comparative experiments are as follows:
[0083] 0.80 g of ethylbenzene was added as an internal standard to the reaction solution (i.e., the reaction system after catalytic hydroxylation of phenol using the TS-1 molecular sieve described above). After mixing thoroughly, a small amount of the solution was centrifuged at 10,000 rpm for 3 min, and the supernatant was then collected for GC analysis. The conversion rate and selectivity of each product were calculated, and the results are shown in Table 1.
[0084] In Examples 1, 2, and 3, the conditions were exactly the same except that the mass of N,N-dimethylformamide in step (4) was 0.632 g, 0.421 g, and 0.842 g, respectively. In Comparative Example 1, the conditions were exactly the same as in Example 1 except that N,N-dimethylformamide was not added in step (4). In Comparative Example 2, the conditions were exactly the same as in Example 1 except that tetrapropylammonium bromide was not added in step (6). In Comparative Example 3, the conditions were exactly the same as in Example 1 except that ethanolamine was not added in step (6). The reaction results are shown in Table 1.
[0085] Table 1
[0086] Conversion rate / % Diphenol selectivity / % Example 1 32.85 98.87 Example 2 31.74 98.61 Example 3 32.16 98.81 Comparative Example 1 13.71 76.81 Comparative Example 2 18.37 93.71 Comparative Example 3 14.92 94.82 <![CDATA[Prior art [2] > 20 90
[0087] [1].Taramasso M.,Perego G.,Notari B.Preparation ofPorous CrystallineSynthetic Material Composed ofSilicon and Titanium Oxides.USPat.4410501,1983.
[0088] [2] Shu Shili, Zhang Shuoxu. Research progress on catalysts for the hydrogen peroxide hydroxylation reaction of phenol [J]. Chemical Bulletin, 2015, 78(08):702-709. DOI:10.14159 / j.cnki.0441-3776.2015.08.005.
[0089] As shown in Table 1, the catalytic performance of the examples, including conversion rate and diphenol selectivity, is significantly higher than that of the comparative examples and the prior art. Specifically, compared with Comparative Example 1, Example 1 exhibits a plate-like morphology due to the addition of N,N-dimethylformamide, thus significantly reducing mass transfer resistance. Therefore, its conversion rate is 2.39 times that of Comparative Example 1, and its diphenol selectivity is 1.28 times that of Comparative Example 1. Compared with Comparative Example 2, Example 1 obtains a plate-like hollow molecular sieve with higher crystallinity due to the presence of TPABr template agent in the post-treatment process, i.e., it has a more complete MFI molecular sieve structure. Therefore, its conversion rate is 1.78 times that of Comparative Example 2, and its diphenol selectivity is 1.06 times that of Comparative Example 2. Compared with Comparative Example 3, Example 1 has higher basicity due to the presence of ethanolamine in the post-treatment process. This is more conducive to the formation and recrystallization of six-coordinate titanium active sites in the post-treatment process, resulting in a large number of hollow structures and six-coordinate titanium species with stronger catalytic activity inside the crystal. Therefore, its conversion rate is 2.2 times that of Comparative Example 3, and its diphenol selectivity is 1.04 times that of Comparative Example 3.
[0090] More importantly, compared to Example 1, Examples 2 and 3 also exhibited superior catalytic performance when the amount of N,N-dimethylformamide added was further increased or decreased. This means that treating the sheet-like TS-1 synthesized using N,N-dimethylformamide with tetrapropylammonium bromide and ethanolamine is beneficial for constructing active sites with highly efficient catalytic performance inside the molecular sieve. This provides important theoretical guidance for the industrial preparation of TS-1 molecular sieves with even better catalytic performance.
[0091] It can also be seen that in step (6) of the method of the present invention, tetrapropylammonium bromide and ethanolamine have a synergistic effect, which can synergistically improve the relevant properties of the prepared product. In particular, tetrapropylammonium bromide and ethanolamine with a mass ratio of 0.383:0.510 have a significant synergistic effect, which can significantly improve the relevant properties of the prepared product. It can also be seen that in step (4) of the method of the present invention, N,N-dimethylformamide and tetrapropylammonium bromide have a synergistic effect, which can synergistically improve the relevant properties of the prepared product. It can also be seen that in step (4) of the method of the present invention, N,N-dimethylformamide and ethanolamine have a synergistic effect, which can synergistically improve the relevant properties of the prepared product.
[0092] Although embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will understand that various substitutions, variations, and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the scope of the invention is not limited to the contents disclosed in the embodiments.
Claims
1. A method for preparing a sheet-like hollow TS-1 molecular sieve for phenol hydroxylation, characterized in that: The synthesis steps include the following: (1) Add tetraethyl orthosilicate dropwise to an aqueous solution containing tetrapropylammonium hydroxide; (2) After the above solution becomes clear, add the solution containing tetrabutyl titanate and isopropanol dropwise to allow for complete hydrolysis; (3) Stir the obtained clear solution in a constant temperature water bath to remove alcohol for 1 hour; (4) After the alcohol removal is completed, N,N-dimethylformamide is added to the resulting solution; (5) The obtained solution was placed in a kettle, and after hydrothermal crystallization, the crystallized product was obtained. Finally, centrifugation, drying and calcination were performed to obtain the parent sheet-like TS-1 molecular sieve. (6) Dissolve the parent TS-1 molecular sieve in an aqueous solution of tetrapropylammonium bromide and ethanolamine to obtain a precursor solution; (7) The obtained solution is placed in a kettle, and after hydrothermal crystallization, a crystallized product is obtained. Finally, it is centrifuged, dried and calcined to obtain a sheet-like hollow TS-1 molecular sieve rich in six-coordinated titanium, which is the sheet-like hollow TS-1 molecular sieve used for phenol hydroxylation.
2. The preparation method according to claim 1, characterized in that: In step (1), the aqueous solution containing tetrapropylammonium hydroxide has a mass concentration of 25%, the water is deionized water, the molar ratio of tetrapropylammonium hydroxide to tetraethyl orthosilicate (calculated as SiO2) is 0.1 to 0.5:1, and the molar ratio of deionized water to tetraethyl orthosilicate is 20 to 50:
1.
3. The preparation method according to claim 1, characterized in that: In step (2), the mass ratio of tetrabutyl titanate to isopropanol is 0.2-0.3:2.0-3.0; in step (2), the mass ratio of tetrabutyl titanate to tetraethyl orthosilicate in step (1) is 1:30-50; and in step (2), the mass ratio of tetrabutyl titanate to tetrapropylammonium hydroxide in step (1) is 1:10-20. Alternatively, in step (3), the alcohol removal temperature is 50–90°C and the dissolution time is 2–6 h.
4. The preparation method according to claim 1, characterized in that: In step (4), the molar ratio of N,N-dimethylformamide to tetraethyl orthosilicate (calculated as SiO2) in step (1) is 0.2 to 1.2:1, and the mass ratio of N,N-dimethylformamide to tetrapropylammonium hydroxide in step (1) is 0.04 to 0.2:
1.
5. The preparation method according to claim 1, characterized in that: In step (6), the mass ratio of tetrapropylammonium bromide to the parent flaky TS-1 molecular sieve is 0.5 to 1.0:1, the mass ratio of ethanolamine to the parent flaky TS-1 molecular sieve is 1 to 2:1, the water is deionized water, and the mass ratio of deionized water to the parent flaky TS-1 molecular sieve is 20 to 40:
1. Alternatively, in step (6), the dissolution temperature is 40–80°C and the dissolution time is 2–6 h.
6. The preparation method according to any one of claims 1 to 5, characterized in that: The hydrothermal crystallization temperature in steps (5) and (7) is 100-200℃ and the time is 24-72h; the calcination temperature in steps (5) and (7) is 500-600℃ and the time is 2-8h.
7. The sheet-like hollow TS-1 molecular sieve prepared by the preparation method according to any one of claims 1 to 6.
8. The application of the sheet-like hollow TS-1 molecular sieve as described in claim 7 in the catalytic hydroxylation reaction of phenol.
9. The method for catalyzing the hydroxylation reaction of phenol using the sheet-like hollow TS-1 molecular sieve as described in claim 7, characterized in that: Includes the following steps: 1) Mix TS-1 molecular sieve, phenol, and methanol evenly in a round-bottom flask; wherein the mass ratio of TS-1 molecular sieve to phenol is 1:10, and the mass ratio of phenol to methanol is 1:
4. 2) Place the round-bottom flask in a water bath and stir at 500-1000 rpm until it reaches 50-80°C. Add hydrogen peroxide to start the reaction at 50-80°C under normal pressure for 4-6 hours. The mass ratio of phenol to hydrogen peroxide is 1:0.
4. 3) After the reaction is complete, cool the mixture rapidly to room temperature in a cold water bath.
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